Prevalence and spatial distribution of Ixodid tick populations in the forest fringes of Western Ghats reported with human cases of Kyasanur forest disease and monkey deaths in South India
Kyasanur forest disease (KFD) is a major tick-borne viral haemorrhagic fever caused by KFD virus (KFDV) (Flaviviridae). The disease was reported to be confined to five districts of Karnataka state India until 2011. During 2012–2016, emergence of KFD has been reported in newer areas of Karnataka and adjoining states. Therefore, survey of tick vectors was carried out in these new areas of Karnataka and adjoining states reported with monkey deaths and human cases of KFD. In all selected sites, ticks from the forest floor were collected by lint clothes using flagging method. Tick samples were tested for KFDV nucleic acid by real-time RT-PCR. A total of 4772 ticks, comprising eight species of genus Haemaphysalis and one species each of genus Amblyomma, Ixodes and Rhipicephalus was collected. Haemaphysalis spinigera, the principal vector of KFDV was the predominant tick species (59.5%) collected followed by H. turturis (8.6%). The abundance of H. spinigera ranged from 9.2 to 33.9 per man-hour in the six districts surveyed. Of 214 (4418 tick samples) pools screened by real-time RT-PCR, two pools of H. spinigera were positive for KFDV. High abundance of Haemaphysalis vectors in the six districts indicated that the districts are receptive for KFD outbreaks. KFDV was detected in the tick vectors in the new foci of the KFD. Data on tick distribution will be useful in creating KFD risk map for strengthening the ongoing preventive measures such as vaccination and supply of insect repellents to the high risk groups and intensive health education.
KeywordsHaemaphysalis species Kyasanur forest disease Ixodidae Western Ghats India
The authors would like to thank the District Health authorities in Malappuram and Wayanad districts for their initiative and support of the investigation. We thank the staff of Karulai PHC, Malapuram district and Pulpally Block CHC, Wayanad district for their support and assistance during the investigation. Our sincere thanks to Chief Wildlife Warden, Kerala, Tamil Nadu and Karnataka State, and District Forest Officers of Wayanad and Malappuram districts of Kerala, Sathyamangalam and Nilgiri districts of Tamil Nadu and Shimoga and Chamarajnagar districts of Karnataka and the forest guards from the respective areas for granting permission and their support during the entomological survey. We also thank Mr. V. Padmanaban, M. Stalin, and A. Ravi from the Division of Vector Biology and Control, Vector Control Research Centre, Puducherry and Mr. Sonawane, and Mr. Dhaigude from National Institute of Virology, Pune for their assistance in the field and laboratory.
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